import java.util.Scanner;

public class Day_35_1_年会抽奖 {
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        while(sc.hasNext()){
            int n=sc.nextInt();
            float sum1=count(n);//每个人都不可能抽中出现的情况
            float sum2=factorial(n);//抽奖可能出现的情况
            float result=(sum1/sum2)*100;
            System.out.println(String.format("%.2f",result)+"%");
        }
    }
    public static float count(int n){
        if(n==1){
            return 0;
        }else if(n==2){
            return 1;
        }else{
            return (n-1)*(count(n-1)+count(n-2));
        }
    }
    public static float factorial(int num){
        float result=1;
        if(num==0){
            return 1;
        }else if(num>0){
            result=num*factorial(num-1);
        }
        return result;
    }

}
